S1) Energy Production I — Carbohydrates Flashcards Preview

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Flashcards in S1) Energy Production I — Carbohydrates Deck (50)
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Define the terms endergonic and exergonic

Exergonic: a reaction where the energy released is greater than the energy input

- Endergonic: a reaction where the energy input is greater than the energy released 


What is the ATP-ADP cycle?

The ATP-ADP cycle is the cycle that couples endergonic reactions with exergonic reactions


What does the ATP-ADP cycle do?

- It allows for the controlled release of energy by oxidation

- Some of the energy is conserved by the formation of ATP from ADP and Pi and the remainder is lost as heat 


What is cell metabolism?

Cell metabolism is the highly integrated network of chemical reactions in distinct metabolic pathways that occur within cells


Define the terms catabolism and anabolism

Catabolism involves the breakdown of larger molecules to smaller ones

Anabolism involves the synthesis of larger molecules from smaller ones


Compare and contrast catabolic and anabolic pathways 

- Catabolic pathways are oxidative, release large amounts of free energy, and produce some intermediary metabolites

- Anabolic pathways are reductive, and use energy and intermediary metabolites from catabolism to synthesise cell components 


Identify the 3 major carrier molecules





Represent the 3 major carrier molecules in their oxidised and reduced forms

- Oxidised forms: NAD+, NADP+, FAD

- Reduced forms: NADH + H+, NADPH + H+, FAD2H


Why must carrier molecules cycle between oxidative and reductive processes to maintain cell function?

To allow for both oxidation reactions (require NAD+) and reduction reactions (require NADH + H+) to occur


What is Free Energy?

Free Energy is the energy released in an exergonic reaction that is available to do work (ΔG) 


What are the four steps in carbohydrate metabolism?

- Stage 1: Breakdown to monomers

- Stage 2: Breakdown to metabolic intermediates 

- Stage 3: TCA (Kreb's) cycle

- Stage 4: Oxidative phosphorylation 


In stage 1 of metabolism, carbohydrates are digested at the salivary glands, pancreas and small intestines

Identify the respective enzymes involved

- Saliva: amylase

- Pancreas: amylase 

- Small intestine: lactase, sucrase, pancreatic amylase, isomaltase


Why can't cellulose be digested by humans?

No enzymes to break down the β 1-4 linkages present in dietary fibres i.e. no cellulase


Identify 3 clinical features of primary lactase deficiency

- Absence of lactase persistence allele

- Only occurs in adults 

- Highest prevalence in Northwest Europe


Identify 3 clinical features of secondary lactase deficiency

- Caused by injury to small intestine 

- Occurs in both infants and adults 

- Generally reversible


Identify four clinical conditions which could cause injury to the small intestine, leading to secondary lactase deficiency

- Gastroenteritis

- Coeliac disease

- Crohn's disease

- Ulcerative colitis 


Describe 3 features of congenital lactase deficiency

Extremely rare

- Autosomal recessive defect in lactase gene 

- Cannot digest breast milk


What foods should someone with a lactase deficiency abstain from?

- Milk 

- Cream

- Yoghurt

- Cheese


Identify 4 symptoms associated with lactase deficiency?

- Bloating/cramps

- Flatulence

- Diarrhoea

- Vomiting 

- Rumbling stomach


How are monosaccharides absorbed?

- Active transport by SGLT1 into intestinal epithelial cells 

- Active transport by GLUT2 into blood supply 

- Facilitated diffusion by transport proteins GLUT1-GLUT5 into cells


Identify 4 tissues which have an absolute requirement for glucose

- Neutrophils 

- Lens of eye

- Red blood cells

- Innermost cells of kidney medulla


Describe the glucose dependency of the brain

The CNS prefers glucose as a fuel but can use ketone bodies for some energy requirements in times of starvation


Where does glycolysis occur?

- Occurs in all tissues

- Occurs in cytosol


What kind of process is glycolysis?

- Exergonic process 

- Oxidative process 


Identify the 4 functions of glycolysis

- Oxidation of glucose

- NADH production 

- Synthesis of ATP (2 ATP per glucose molecule)

- Produces C6 and C3 intermediates (no loss of CO2)


Identify the enzymes at point 1, 3 and 10

1 - Hexokinase 

3 - Phosphofructokinase-1

10 - Pyruvate kinase 


Describe Phase 1 of Glycolysis (reactions 1-3)

- Phosphorylation of glucose to G-6-P 

- Polarised glucose is more reactive & cannot return down plasma membrane

- Input: 2 moles ATP per mole glucose 


Describe Phase 2 of Glycolysis (reactions 4-10)

- Reaction 4: C6 --> 2C3 units

Reaction 6: Reducing power captured (NADH)

- Reaction 7&10: ATP synthesis (substrate level phosphorylation)


Identify the irreversible reactions in glycolysis

Large -ΔG:

- Reactions 1

- Reaction 3

- Reaction 10


Explain the allosteric regulation of glycolysis by phosphofructokinase

Allosteric regulation (muscle):

- Inhibited by high ATP

- Stimulated by high AMP